Faster and more powerful computer components allow the design and construction of higher performance portable computing devices such as laptop or notebook computers. Unfortunately, the use of such faster and more powerful computer components often results in increased heat generation by such computing devices.
Additionally, as some computer components shrink and/or increasing computer component integration shrinks overall computer size, electronic components may be arranged in a more compact form. Such increasing component density coupled with decreasing overall computing device size inherently decreases space available for convective airflow and accordingly raises heat dissipation concerns. Thus, improved heat dissipation technology is often needed to maintain operating temperatures within an acceptable range in smaller and/or more powerful portable computing devices.
A portable computing device typically includes a base and a screen which are rotatably attached by a hinge. The base usually has an input device such as a keyboard or a touchpad as well as a number of electronic components. Integrated circuits with the highest clock frequency are typically located in close proximity to each other within the computer base.
Many heat generating computer system components take the form of integrated circuits. Such integrated circuits are typically mounted on a motherboard or another circuit board within the base of the portable computer device. A processor is one component that generates a large amount of heat in a typical computing device. Other electrical components which also generate heat include memory circuits, power supply circuits, and circuit boards such as a video card.
Maintaining operating temperatures of computer system components below certain levels is important to ensure performance, reliability, and safety. Most integrated circuits have specified maximum operating temperatures, above which the manufacturer does not recommend operation. Transistors, the building blocks of integrated circuits, tend to slow down as operating temperature increases. Thus, a computer system that operates its integrated circuits close to or beyond recommended timings may fail as temperature increases.
Additionally, integrated circuits may be physically damaged if temperatures elevate beyond those recommended. Such physical damage obviously can impact system reliability. Finally, the computer system casing should be kept at a temperature which is safe for human contact. This may necessitate spreading of heat throughout a computer system base or efficiently expelling heat to avoid hot spots near certain components such as a processor.
Typically, heat sinks, fans, and heat pipes are employed to dissipate heat from integrated circuits and other electronic components. Increases in heat generation are often accommodated by simply increasing the quantity or size of these heat dissipation elements. The relatively small size of a portable computing device, however, complicates heat dissipation by limiting airflow, crowding heat generating components, and reducing the space available for heat dissipation devices.
The small size of a portable computing device particularly restricts the use of cooling fans. As is illustrated in FIG. 1, a prior art integral blade fan 150 is typically mounted at an external surface of a portable computing device 105. The fan is an integral blade fan, meaning that the fan blade 155 is integrally formed with, or at least attached to, the rotor portion of the motor 160, and the blades extend axially with the motor in the center.
As illustrated, the fan 150 is mounted in the plane of a side wall 120 of the base of the portable computing device. The side wall 120 is typically used as a vent since the lower surface of the device may be blocked by the surface upon which the device is resting, and the upper surface typically houses a keyboard and may be blocked by the display (when the device is closed) or other objects resting on the-device. The side or back of a computing device normally remains unobstructed during operation of the device and is accordingly a better candidate for fan mounting.
One shortcoming of such integral blade fans is that the circumference of the motor limits the blade size since the total fan height is fixed by the form factor of the computer (i.e., the height of side wall 120). Unfortunately, the rapidly shrinking dimensions of portable computing devices have not been accompanied by similar reductions in motor dimensions. As a result, cooling fan blades may need to be downsized, and/or integral blade cooling fans may need to be eliminated, typically resulting in less cooling capacity. Such decreased cooling capacity may prove unacceptable since electronic components which use increasing amounts of power and/or are packaged in a more compact fashion may require the same or increased heat dissipation. Thus, the prior art integral blade fans may no longer continue to meet cooling needs for computing devices.